The invention relates to monolithic integrated circuit (IC) chips which are designed to shut down when their temperature exceeds a predetermined maximum. Typically, in the prior art, a chip temperature limit of about 160.degree. C. is employed to activate a trip circuit, the output of which will turn off or lock out the chip operation. Thus, an overload will shut down the circuit which will then proceed to cool off. Upon sufficient cooling the circuit will again be energized and normal operation will occur. However, if the overload condition still exists the chip will again heat up and be shut down. Thus, thermal cycling will continue until the circuit power supply is removed or until the overload either is cleared or goes away on its own. In some applications such cycling can be detrimental. For example, in a motor control circuit application a thermal shutdown will stop motor action and a human operator might then reach into the machinery. An unexpected start up can then be disastrous. Accordingly, it is desirable under some conditions to include a latch function that will hold the IC chip inoperative until the circuit is deliberately reset. In this instance, a package pin is coupled to the thermal shutdown circuit to provide a flag that shows or indicates when a shutdown has occurred. Typically, another pin would be employed to provide an electrical reset for the shutdown function. It would be desirable to employ a single pin to provide both the indication and control of shutdown. Under this condition the same pin can be employed to "strap out" the thermal shutdown function.
In a copending patent application by Robert A. Pease, U.S. Ser. No. 236,110, filed 8-22-88, and titled LOW VOLTAGE LOCKOUT CIRCUIT, an IC is disclosed in which a portion of the chip heat-producing circuits can be locked out or their function terminated in response to low supply voltage. The teaching in this patent application is incorporated herein by reference.